The present invention relates to saws and other cutting and machining tools which have their cutting or machining surfaces coated with polycrystalline cubic boron nitride (PCBN) and/or which have PCBN tips (strips or inserts) mounted on their cutting or machining surfaces for the purpose of cutting and/or machining hard materials such as Hardiplank(copyright). More specifically, the present invention relates to the use of PCBN in the cutting and machining operations of Hardiplank(copyright) and other hard building materials which are cement and/or mineral based.
Many hard materials have been developed especially for use in the home building industry. Many of these materials are Portland cement based materials and include other additives such as ground sand, cellulose fibers and the like. One such product is Hardiplank(copyright) manufactured by the James Hardie and Coy Pty Limited. The product is used as a replacement for conventional sidings used in homes. Hardiplank(copyright) is a cement based plank comprising Portland cement, ground sand, cellulose fibers, additives and water. A typical Hardiplank(copyright) plank has a length of about 12 feet, a width anywhere in the range of about 6 to 12 inches, and a thickness in the range of about {fraction (5/16)} to xe2x85x9c inch.
One typical saw blade used to cut such material is a circular steel blade. The saw blade consists of radial teeth formed around the circumference of the saw blade. Carbide tips are bonded on the leading edges of the teeth. As the saw blade rotates during cutting, the carbide tips engage the material and cut through it. Current carbide tipped saw blades are unsuitable for cutting Hardiplank(copyright). For example, in one test, a saw blade with carbide tips was able to make only about 30 cuts on Hardiplank(copyright) planks prior to failing. In other words, after 30 cuts, the carbide tips needed re-sharpening or replacement. A cut is typically a cut of about 6 inches through a xe2x85x9c inch Hardiplank(copyright) plank.
It is expected that bonding polycrystalline diamond (xe2x80x9cPCDxe2x80x9d) tips instead of carbide tips to a blade will increase the cuts achieved by the blade. It is also expected that when used to cut Hardiplank(copyright), a circular saw blade with PCD tips will have an operational life that is 100 times as great as the operational life of a saw blade with carbide tips. The problem with using PCD tips, however, is that they require special machine tools for grinding the PCD tips to a desired shape. As such, the manufacturing costs of PCD tips and similarly for PCD coatings for use with cutting and machining tools for cutting cement based materials such as Hardiplank(copyright) may be excessive.
Therefore, tips and coatings are needed that would improve the operating lives of the cutting and machining tools used for cutting and machining hard cement and/or mineral based materials such as Hardiplank(copyright), and that can be ground and sharpened using the machine tools used to grind the current carbide tips and coatings.
Cutting tools and machining tools are provided having PCBN tips bonded to their cutting or machining surfaces or having their cutting or machining surfaces coated with PCBN. More specifically, the present invention is directed to using PCBN, and preferably PCBN having a high volume content of CBN, for cutting or machining cement and/or mineral based hard building materials such as Hardiplank(copyright).